In a telecommunication system, subscriber lines are generally connected to a Public Switched Telephone Network (PSTN) via access network devices. Typically, access devices include channel interfaces for terminating the subscriber lines and a network interface for connecting the access device to a local exchange switch of the PSTN. The PSTN is connected to the network device using one or more wide-band carrier links. The access device converts data between an analog signal used on subscriber lines and a digital signal typically used by the PSTN so data can be transported over the network. This conversion involves operations such as sampling and digitizing voice-band signal from each of the subscriber lines and aggregating the digitized signals from the plurality of lines into a single signal for transporting, so the information can be transported more efficiently on the wide-band carrier links.
Primarily, telecommunication systems have been implemented using time-division multiplexing (TDM) as the carrier technology of choice. TDM technology divides the available bandwidth into timeslots and assigns a predefined timeslot to each subscriber line. The subscriber line transmits its data to the network during its assigned timeslot. As such, existing access devices normally provide a TDM interface to the network in the form of T1 or T3 carrier links. However, as the amount of data traffic travelling over public packet networks outgrows voice traffic, new access devices have become available which provide connectivity to next-generation packet networks, thereby enabling call services to be provided over a packet network.
However, although a trend is developing towards next-generation packet network to provide voice communication, there are still many legacy systems that are reluctant to make such a switch. This reluctance is because packet network access devices are designed solely for packet network access. Thus, this limitation has left service providers with an obligation to keep and maintain legacy access equipment in parallel with next-generation access equipment, and follow a costly and inefficient migration path that requires physically moving subscriber lines from the legacy equipment to the packet-network access device. This difficulty discourages service providers from adopting next-generation packet networks, thereby delaying the introduction of new call services that a packet-based infrastructure would make possible.
Therefore, it is an object of the present invention to obviate or mitigate at least some of the above-mentioned disadvantages.